In the fabrication of semiconductor devices, various structures such as metallization layers, passivation layers, insulation layers, etc. are formed on a substrate. The quality of the semiconductor device fabricated is a strong function of the processes with which these structures are formed. The quality is also a function of the cleanliness of the manufacturing environment in which the substrate is processed.
Technological advances in recent years in the increasing miniaturization of semiconductor circuits necessitate more stringent control of impurities and contaminants in the processing chamber of the semiconductor device. When the miniaturization of the device progresses to the submicron level, the minutest amount of contaminants can significantly reduce the yield of wafers. For instance, the presence of particles during deposition or etching of thin films can cause voids, dislocations or short-circuits which adversely affect performance and reliability of the devices.
Particle and film contamination has been significantly reduced by improving the quality of clean rooms and by automated equipment designed to handle semiconductor substrates, and also by improving techniques used to clean the substrate surfaces. However, many particles are generated and film contaminated inside substrate processing chambers themselves. Possible sources of contamination include processing materials, interior walls of processing chambers, and the mechanical wear of the automated substrate handling equipment.
In processing equipment that uses plasma enhancement, many chemically reacted fragments of various kinds are generated from the processing gases which include ions, electrons and radicals. The fragments can combine to form slightly negatively charged particles which may ultimately contaminate a substrate being processed. Additionally, various materials such as polymers are coated onto the process chamber walls during plasma processing. Mechanical and thermal stresses may cause these materials to fracture and dislodge from the walls and generate additional contaminant particles. Other possible sources of contaminants are oil from vacuum pumps, and particles generated within the processing chambers during substrate transfer operations.
The techniques of in-situ cleaning of process chambers have been developed in recent years. Various kinds of cleaning gases such as nitrogen trifluoride, chlorine trifluoride, hexafluoroethane, sulfur hexafluoride and carbon tetrafluoride and mixtures thereof have been used in various cleaning applications. These gases are flowed into a process chamber at a predetermined temperature and pressure for a desirable length of time to clean the surfaces inside a process chamber. However, these cleaning techniques are not always effective in cleaning or dislodging all the film and particle contaminants coated on the chamber walls. The minutest amount of contaminants left over from such cleaning process can cause significant problems in the subsequent manufacturing cycles.
It is therefore an object of the present invention to provide an improved in-situ cleaning method for surfaces inside a process chamber that does not have the shortcoming of the prior art cleaning methods.
It is another object of the present invention to provide a novel in-situ cleaning method for surfaces inside a process chamber that can be carried out without a significant process change or equipment modification.
It is a further object of the present invention to provide a novel in-situ cleaning method for surfaces in a process chamber of film and particle contaminants by using a magnetic field spiking technique.
It is yet another object of the present invention to provide an improved in-situ cleaning method for surfaces inside a process chamber equipped with plasma enhancement by providing a magnetic field inside the chamber and means to switch on and off such magnetic field.